1. Field of the Invention
The present invention relates to a method of taking out a lead of a semiconductor tip part.
2. Description of the Prior Art
Recently, such as in an electrode for measuring ion concentration like pH, in order to reduce the size of the electrode as a whole, to reduce the cost of production, and to improve the operation and maintenance, the electrode has been constructed in the form of a sheet.
For example, a sheet-type pH-measuring electrode has been constructed by screen printing a silver paste on the surface of a substrate formed of PET (polyethylene terephthalate), which is highly insulative and inexpensive, to form an electrode and a wiring pattern. A part of the electrode is coated with AgCl to form an internal electrode portion, and a pH response membrane formed of flat plate-like response glass is affixed to the internal electrode portion through a gelatinized internal solution (for example, Japanese Utility Model Application No. 191497/1986 filed by Horiba, Ltd.).
Since the pH response membrane has a large electric resistance and a minute electric current is used as an input, the measurement is apt to be influenced by outside noise. Therefore, it is necessary to incorporate in the PET substrate a MOSFET having a large input impedance before an amplifier for amplifying a signal from the pH response membrane.
A method of incorporating a semiconductor tip part such as the MOSFET and taking out a lead includes a wire bonding method, a flip-tip method, a beam lead method, a tape carrier method and the like.
The wire bonding method has problems in that a lead portion is wanting in mechanical strength. The reliability is also low and is restricted by an increased absorption of vibration for a comparatively soft substrate such as PET substrate and is remarkably difficult for ultrasonic bonding. Methods such as the flip-tip method are highly reliable but have a disadvantage in that the manufacturing process is complicated and the cost of production is high.